The present disclosure relates to an image reading device that reads an image of an original document and an image forming apparatus.
In image reading devices, when an original document is placed on contact glass and a document pressing plate is closed, a document size detector detects the size of the original document. Upon power-up or recovery from a sleep state of such an image reading device, shading correction through gain adjustment or offset adjustment of an image sensor is performed for preparing image reading. In a certain image reading device, when an original document is set and the document pressing plate is closed during gain adjustment or offset adjustment, the currently performed gain adjustment or offset adjustment is suspended and document size detection is performed.